[actor] Force a relayout on set_parent()

[actor] Force a relayout on set_parent()

The current code that handles the invariant that the new parent
of an actor needing a layout should also be queued for relayout
is hitting the short-circuiting we do in the queue_relayout()
method.

In order to fix this we can forcibly set the actor to need a
width/height request and an allocation; then we queue a relayout
on the parent.

Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>